1. Field of the Invention
The present invention relates to a data communication network, and particularly to a broadcast method in a data communication network for broadcasting changes in status of network users to concerned destinations within the network when such changes occured.
2. Description of the Related Art
An example of this type of broadcast method of status change by each user's processor in a data communication network is disclosed in, for example, Japanese Patent Application Laid-open No. 230363/90 (filed Sep. 12, 1994). Here, each of the processors connected to a common transmission medium detects status changes of each I/O device, and transmits and receives configuration information indicating each I/O status by way of the common transmission medium, thereby performing mutual diagnosis of I/O status. A transmission medium control device (Network Control Processor) performs control when the connected processor transmits and receives data by way of the common transmission medium. When a processor is activated, the processor detects I/O status changes that it monitors, (it detects values differing from initial values previously stored in nonvolatile memory), and broadcasts its own configuration information by way of the common transmission medium. In this way, each user can detect mutual configuration information even at the time of system reconfiguration due to recovery of the processor or NCP.
The above-described broadcast method of the prior art broadcasts each change in user status event completely, notifying each concerned destination associated with the user until each has been notified. New notification of subsequent changes in user status are held in a FIFO queue as long as resources are available for use, and if there is not sufficient resources for holding these changes in user status information, new information may be lost. In addition, since user status may change during the period from the time the broadcast decision is made until the time broadcast begins, invalid information may be proliferated in the network. In other words, when broadcast registration and broadcast processing are executed sequentially and without suspension, because notification of subsequent changes in user status will be left at the end of the FIFO queue, the impact of new information will not be reflected in the broadcast processing underway or in processes which have been previously enqueued.
Another problem is that changes in user status often occur in groups rather than evenly. This phenomenon raises the two problems that, when a large number of changes in user status occur at the same time, the broadcast process will monopolize the resources at the originating destination, interfering with the performance of other normal functions, and the sudden increase in broadcast messages will cause network congestion.